From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from [140.186.70.92] (port=47616 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1OY1lC-0007Ae-UH for qemu-devel@nongnu.org; Sun, 11 Jul 2010 15:00:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.69) (envelope-from ) id 1OY1lB-0003LR-Mg for qemu-devel@nongnu.org; Sun, 11 Jul 2010 15:00:18 -0400 Received: from mx1.redhat.com ([209.132.183.28]:23326) by eggs.gnu.org with esmtp (Exim 4.69) (envelope-from ) id 1OY1lB-0003L9-FG for qemu-devel@nongnu.org; Sun, 11 Jul 2010 15:00:17 -0400 Date: Sun, 11 Jul 2010 21:54:56 +0300 From: "Michael S. Tsirkin" Message-ID: <20100711185456.GA11048@redhat.com> References: <20100711180910.20121.93313.stgit@localhost6.localdomain6> <20100711180936.20121.35376.stgit@localhost6.localdomain6> <4C3A09F3.8010304@redhat.com> <1278872784.20397.18.camel@x201> <4C3A0DE3.8010806@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <4C3A0DE3.8010806@redhat.com> Subject: [Qemu-devel] Re: [RFC PATCH 4/5] APIC/IOAPIC EOI callback List-Id: qemu-devel.nongnu.org List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Avi Kivity Cc: chrisw@redhat.com, Alex Williamson , qemu-devel@nongnu.org, kvm@vger.kernel.org, pugs@cisco.com On Sun, Jul 11, 2010 at 09:30:59PM +0300, Avi Kivity wrote: > On 07/11/2010 09:26 PM, Alex Williamson wrote: > >On Sun, 2010-07-11 at 21:14 +0300, Avi Kivity wrote: > >>On 07/11/2010 09:09 PM, Alex Williamson wrote: > >>>For device assignment, we need to know when the VM writes an end > >>>of interrupt to the APIC, which allows us to de-assert the interrupt > >>>line and clear the DisINTx bit. Add a new wrapper for ioapic > >>>generated interrupts with a callback on eoi and create an interface > >>>for drivers to be notified on eoi. > >>> > >>You aren't going to get this with kvm's in-kernel irqchip, so we need a > >>new interface there. > >Registering an eventfd for the eoi seems like a reasonable alternative. > > I'm worried about that racing (with what?) With device asserting the interrupt? Need to make sure that all possible scenarious work well: device asserts interrupt driver clears interrupt device asserts interrupt eoi device asserts interrupt driver clears interrupt eoi device asserts interrupt etc Not that I see issues, these are things we need to check. > >I also need to figure out how to avoid bouncing the vfio interrupt > >events through qemu, but it's a functional start. Thanks, > > I thought the scheduler has/wants to have something that moves the > irq to whatever thread it wakes up. With irqfd, it would flow > naturally. > > -- > I have a truly marvellous patch that fixes the bug which this > signature is too narrow to contain.